The SIM card is a type of smart card used in digital GSM (Global System for Mobile Communications) cellular that stores user data and allows GSM mobile phones that are identified with mobile telephone network providers.
The devices that make use of mobile phone networks are now adapted to accommodate at least one SIM card. However, when they are sold, the SIM card, in general, is not included in them. The card must be purchased by the user in any of the providers. Once it is with the user, the SIM card must be inserted in the device so that they begin to provide all communication services related to the network.
The SIM cards currently available need to be included in the communication device, which presents the following disadvantages:                When a device with a SIM card is stolen or lost, all the information contained in the same is lost;        The user, in losing or forgetting the device somewhere, is not able to make use of his phone number or personal information such as contacts;        For a device to make use of more than one SIM card, it is necessary that it has two or more physical connectors to fit different cards. The manufacturing cost increases too much as such connectors are added;        when the battery of the device ends and the user wants to make use of a borrowed device, or the user uses the borrowed device, or it is necessary to open the devices to change the SIM cards;        While connected, the communication device literally holds the SIM card chip set, which increases battery consumption;        In case of prepaid phone numbers, recharging is done at ATMs of banks or supermarkets, and the user must enter the phone number openly, making it possible that this number is obtained by the bad people.        
An RFID system consists basically of two parts:                A transceiver, also called “reader” that reads a signal and transfers the information to a device that will process it, and        A transponder, which is commonly implemented as an RF tag (radio frequency), which should contain the information to be transmitted to the reader. Physically, a transponder has dimensions of only a few millimeters and the reader can maintain communication generally at distances less than 1 meter.        
The patent document WO2006137740, published on Dec. 28, 2006, owner: TELENOR ASA, reveals a method and system for acquiring information related to a transponder (RFID tag) read by a mobile phone, comprising an RFID reader and an identification and authentication module (SIM card). When the RFID reader reads data from the RFID tag, the identifier and content data are processed and transmitted to a local network for further processing and distribution of supplementary information related to an RFID tag. The SIM card includes a WLAN transmitter and the transmission of the identifier is via the WLAN. According to the teachings of that document, the transponder is on the phone, the SIM card and the transponder are in the device B, which contained information “written” in the transponder transmitted to the SIM card.
The International application WO2009127159, published on Oct. 22, 2009, owner: QUANRAY ELECTRONICS SHANGHAI, describes a dual-interface SIM card and a radio frequency identification system using the same, in which the radio frequency identification system comprises at least a reader and a signal booster. The signal booster is used to relay signals and enhance between the dual interface SIM card and reader, and reader is employed to send command signals to the dual interface SIM card and receive a reply from the dual interface SIM card by the signal booster. The dual interface SIM card and the radio frequency identification system successfully apply a mobile communication equipment to an RFID system, thus making contactless radio frequency, short-distance, low cost identification. According to the teachings of said document, the SIM card is on the phone and the reader communicates with the SIM card.
The document European Patent EP1536573, published on Jun. 1, 2005, owner: SAMSUNG ELECTRONICS CO LTD, disclosures a mobile terminal having a smart card (SIM Card), coupled to an RFID tag and method for performing RFID function in this terminal. It is disclosed a mobile terminal equipped with a smart card coupled with RFID tag and a method for performing RFID function in a mobile terminal. The smart card includes a user information processing section for storing of user information and generating a signal of user information, including user information, an information processing section for storing RFID data and generation of a RFID sign, including RFID data and a main calculating section connected to the processing of user information section in order to control generation and transmission of an user information signal and connected to the RFID information processing section in order to command a generation and a transmission of the RFID signal. When the RFID tag detects an approach of an RFID interrogator, the RFID tag of a CPU requests the smart card to play the role of RFID. Thus, the CPU of the smart card transmits a transition signal so that a processor of the mobile terminal indicates a transition mode in an RFID mode. Then, the RFID function is performed. According to the teachings of said document, the transponder is on the phone, that is, the SIM card and the transponder is in the device B. Thus, when the device with the reader is near the phone, the smart phone becomes an intelligent transponder, since it has all the processing power of the phone with it. It is also described that the mobile phone operates in two modes: phone mode or transponder mode.